Electron-discharge apparatus.



A. W. HULL.

ELEGTRON DISCHARGE APPARATUS.

APPLICATION FILED DEC 29,1913.

1,1 14,697, Patented Oct.20,1914.

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ALBERT W. HULL, OF WORCESTER, MASSACHUSETTS,

TRIO COMPANY, A CORPORATION OF ASSIGNOR TO GENERAL ILEG- NEW YORK.

` ELECTRON-DISCHARGE APPARATUS.

Specification of Letters Patent.

Application led December 29, 1913. l Serial No. 809,249.

To all whom 'it may concern Be it known that I, ALBERT W. HULL, a citizen of the United States, residing at Worcester, county of Worcester, State of Massachusetts, have invented certain new and useful Improvements. in Electron-Discharge Apparatus, of which the following is a specification.

The present invention relates to electrical apparatus in which electrical energy is transmitted or conveyed across an evacuated space by negative charges or particles of electricity known as electrons.

Electrons are emitted by 'materials when at incandescence-and also by-various metals, particularly the alkali metals, when illuminated by ultraviolet rays. When a voltage is impressed upon an incandescent body at a su ciently high temperature, making it the cathode and another conductor -the anode, a discharge will pass through an intervening evacuated space which varies directly with the 3/2 power of impressed voltage providing the gaseous pressure in the space is below the minimum at which appreciable gas ionization by collision with the moving electrons can take place. The electron discharge is independent of the vacuum and is characterized by the entire absence of luminous manifestations such as glow in the exhausted space and fluorescence of the glass envelop. As each of the electrons is surrounded by a negative electrostatic field, and also when in motion by a magnetic field, the motion of the electrons is subject to the influence of electromagnetic and electrostatic forces. For this reason each of the electrons in a given space is influenced by the field of all the other electrons in this space, an effect which hereinafter will be referred to as the space charge. y

It is one of the objects of the present invention to reduce the effect of the space charge in an electron discharge device without sacrificing the efficiency of the device.

With this object in view an electron discharge is produced within a positive field, which may be made of very high potential, and the electrons are prevented from dis'- charging themselves upon the conductor by which the positivev field is established by an electromagnetic eld which is parallel to a line joining the anode and the 4cathode ory lwhich the lead parallel to the discharge path and thus confines the motion of the electrons within a predetermined zone. The positively charged conductor thus increases the electron discharge current by eliminating the effect of thlef space charge without taking energy itse My invention will be more clearly understood by reference to the following description taken in connection with the accompanying drawings in which- Figure 1 illustrates diagrannnatically a device embodying my invention lsuitable particularly for amplifying, or detecting minute currents; Fig. 2 illustrates a modification suitable for converting direct current to alternating current, and Fig. 3 illustrates a modification in which two magnetic fields at right angles to each other are used in a devic As shown in Fig. l a discharge apparatus may comprise a cylindrical container l consisting of glass,'quartz or other suitable non-conducting material. Referring to the modification shown in Fig. l, the electron emitting cathode 2 in this particular case consists of a straight wire of highly refractory material, such as malleable tungsten, locatedin the axis of the envelop. It is maintained at incandescence by current supplied by leading-in wires 3 and 4- sealed into the wall of the container in the usual way and is kept taut by a light helical spring 5. The anode 6 has a perforation through Wire 4 passes. It consists also of highly refractory material, preferably tungsten. The anode is very completely freed from gas by electron bombardment in the preparation of the device, as described in an application filed on October 1G, 1913, by Dr. Irving Langmuir, Ser. No. 795,610. The space within the envelop is exhausted to a very low pressure at which gas ionization is substantially absent, preferably by means of a Gazde molecular pump. The particular pressure depends somewhat upon the voltages and currents to be transmitted, and may be as low as a few hundred thousandths of a millimeter of mercury and preferably even lower.

The cathode 2 is surrounded by a conductor 7 which preferably consists of a closely wound spiral of wire extending linearly at least as far a"s"'the cathode and Patented Oct. 20,1914.4

located close to the wall of the; envelop. The conductor 7 in some cases may assume the form of a cylindrical shell of metal, or even a metal deposit on the inner surface of the envelop l. This conductor 7 is connected to a positive terminal of some suitable source 8 of potential such as a battery 8, the negative terminal of which is connected to the cathode. In order to give the conductor 7 a potential gradient similar to that of the filament its terminals preferably are connected to a battery 9, the potential of which is adjusted to make the field potential the same as that of the filament at any two opposite points. The cathode conductor is maintained at incandescence by means of any suitable source of energy, for example, a battery 10, connected to its terminals by conductors 11 and 12. Between the cathode 2 and the anode 6 is connected a local source of energy, such as a battery 13, the positive terminal of which is connected to the anode. Included in lthis local circuit is a detecting device 14, for example, a telephone receiver or anyelectromagnetic responsive device, such as an electromagnetic relay.

In a device thus constructed let it be assumed that a potential is impressed between the cathode and the anode by the source 13. In this case a continuous Iilow of electron current will take place across the evacuated space between the cathode and the anode. As already indicated this current with a given voltage is limited and reduced by the space charge, the value of which in any particular case is dependent upon the geometrical shape of the electron discharge, the dis` tential of the positive charge. In this case,

the electron current would in part pass to conductor 7, which would then act as anode and reduce the efficiency of the apparatus depending upon the degree of its charge.

In accordance with my invention the discharge of the electrons upon the positively charged body, which may be called a neutralizer, is prevented by surrounding the apparatus with a magnetic' coil 15 which when suitably energized establishes an electromagnetic eld parallel with the cathode 2. This ield constrains the electrons to move in curved paths around the cathode, returning to the cathode when no potential is impressed between the cathode and anode, but otherwise revolving in spirals wound around the cathode until they reach the anode. By varying the potential of the positively charged neutralizer 7, the discharge current may be varied with a .sufficiently high temperature of the filament.

The described device'may be used for the1 detection of electromagnetic waves. For example, signals received by'the grounded antenna 1G may be im ressed by means of a loosely-coupled trans ormer 17 upon a tuned resonant circuit 18, containing a condenser 19 and the signals of desired frequency superimposed upon the positive potential of the conductor 7. When the impressed charge is positive the electron current is increased and whenthe-charge is negative, the electron current is decreased. This variation of current may be used to operate the detector 14. Across the terminals of the detector a condenser 20 may be connected to absorb the high frequency oscillations. The electrons leave the cathode with different velocities, the greatest number having the lesser velocities. Hence, the increase of elec tron current will not be proportional to the increase of positive potential on the neutralizer but will increase very rapidly with an increased voltage and fall oft' slowly when the voltage decreases. It should be observed that the source of positive potential 8 contributes no power as the electrons are not permitted to reach the neutralizer 7.

In the modification illustrated in Fig. 2 an alternating potential is impressed upon a conductor 21 which in this case is a cylindrical metallic shell adjoining the walls of the container 1. The cylindrical shell 21 preferably has an annular end portion 22 which is arranged substantially at right angles to the axis of the tube so as to exert a comparatively large component of electric force parallel to the cathode 2. The alternating current source 23 may be a dynamo, transformer, oscillator or the like and may be of high potential. The apparatus is also provided with a solenoid 15 for establishing a magnetic field as already described in connection with Fig. 1. When the conductor 21 is made positive, a comparatively large electron current will iiow to the anode 6 in a manner similar to that already described above, but when the conductor 21 is negative the negative charge coacts with the negative space charge to drive the electrons back into the cathode so that little or no current comes to the anode in spite of the electric field between the anode and the cathode. Thus a pulsating current furnished by the generator 24 will How in the electrode circuit 25 and may be used for any desired purpose. In the figure it has been shown as flowing through the primary of a transformer 26. The sec.

Y Luana? neutralizer is preferably provided with .fan

annular end portion at right angles with the axis of the tube, thus accelerating the motion of the electrons toward the anodes 29, 30. The electrons are prevented from discharging themselves upon the neutralizer 28 by the magnetic field of surrounds the discharge tube and which constrains the electrons into a beam radially through the tube. By means of a magnet 32 which exerts a magnetic force at right angles to the force exerted by magnet 3l a resultant magnetic field may be created so as to direct the electron stream to either anode 29 or anode 30 as desired. The magnetic field of magnet 32 may be generated by a source 33 of alternating current which is connected to windings 34 and 35 of the magnet by conductors 36 and 37 as indicated.

When the anodes 29, 30 are connected by means of conductors 38, 39, to the opposite terminals of a. transformer primary 40 and a direct current generator 41 is connected respectively to the cathode 27 anda neutral point on the transformer primary by conductors 42, 43, an alternating current will pass through the transformer primary having frequency equal to fthat of fthe frequency of the source 33. In other words,

with one-half wave of alternating currentl the magnetic field produced by magnets 31, 32 will deflect the electron stream, say, to anode 29, and thus in one direction through one-half of the transformer primary and with the next half wave of the alternating current the electron discharge will be received by the anode 30 and will thus pass in an opposite direction to the other half of the transformer primary. The source of the direct current 41 may be of very high potentiahfor example, apotential of' 100,000 volts but as soon as current begins to flow frein the cathode to one ot' the anodes and does work in the external circuit the voltage between the cathode and the anode drops to a low value so that the electrons are retarded as they pass through the tube and therefore do not reach the anode with a velocity high enough to cause excessive heating at the anode. It will be observed that in this modification of my invention as well as in the other modifications the positive potential upon the conductor surrounding the cathode is not discharged and the source 44 does no work. While devices of the character described may be used with very high voltages, the greatestadvantage is secured at mode-rate voltages as it is at moderate voltages thatthe current reducing effect of space charge has the greatest effect on the efiiciency.

While I have described certain specific apparatus for carrying out my invention, it should be understood that I do not consider my invention limited thereto. Various modi- Yof my (invention. j `form, and-location 'ofthe cathode the solenoid 31 which` 'mage/'veil be locate at I claim Vasnewand desire totsecureL passing` 4 i by Letters Patent of .mg said cathode, means I cations lwill suggest themselves and' may be 'made withoutf'de or example, the size, may be varied,y and electron emitting cathodes other than lincandescent.,cath'odes may be used. The neutralizer ma d, outside the envelop.

the United States, is 1. An apparatus operating with a substantially pure electron discharge, comprising an evacuated container, an electron-emitting cathode, an anode, ma etic means for confining the electron disc arge from said cathode into a beam of definite radius, means external to-'said cathode and said discharge for establishing a positive electric field to reduce the current-limiting effect of space charge.

2. An apparatus operating with a substantially pure electron discharge, comprising an envelop inclosing a space exhausted arting from the spirit be varied inform andi:

to a pressure below the value at which substantial gas ionization can occur, an electron-emitting cathode, an anode, means for establishing a positive static field around said cathode and a magnetic means external thereto for setting up a magnetic field parallel tol a line joining the anode and the cathode.

3. The combination of a highly evacuated envelop, an yelectron-emitting cathode axially disposed therein, a conductor surroundfor charging said conductor positively with respect to said cathode, a discharge-receiving anode located at one end of said envelop, and means for establishing a magnetic field parallel to said cathode. v

4. An electron discharge apparatus comprising the combination of an envelop, inclosing an evacuated space, an electronemitting cathode anda gas-free anode therein, means for establishing a positive electric field having a component parallel to a line joining the cathode and the anode and also a. component radial about said line, and means for establishing a magnetic field parallel to a line joining the cathode and anode.

5. The method of controlling an elect-ron discharge which consists in subjecting the discharge to a magnetic field and astatic electric field, having a component parallel to the magnetic field and another component radial about said field, and varying one of said elds to vary the electron discharge.

6. The method of controlling an electron discharge from an incandescent cathode to an anode in an evacuated space which consists in subjecting the discharge to a positive static electrical field and a magnetic field parallel to a line joining said cathode and anode and varying one of' said fields to vary the electron discharge.

7. The method of increasing the electi'on In witnese whereofel have herentvset current between an elect'on ellniing cathode my hand this22-day lof December 1913.

and a. coperating ano e W 1c -conslsts in i j' neutralizing the 'negative space charge f *ALBERT W' 5 around said cathode b a. osi-tive charge Witnesses:

andmagnetically directlng t e electron 0111- ROBERT N; WALKER, rent to the anode. ANNIE T. SHORE. 

